Glossary of Terms

Below we have outlined a simple glossary of eye conditions, to assist with your basic guide to common eye conditions.

Age-related macular degeneration (AMD) is a degenerative disease of the central retina, occurring most often in people over age 50 years.

Astigmatism occurs when the front surface (cornea) of the eye is more oblong than round in shape. This prevents the light being focused in the correct way and leads to blurred vision. Astigmatism can usually be corrected with spectacles or contact lenses.

Blindness as defined by the World Health Organization is less than 3/60 in the better seeing eye (see Visual Acuity). Australian population surveys define blindness as less than 6/60 in the affected eye.

Cataract is a cloudiness of the lens inside the eye which reduces the amount of light able to enter the eye, leading to reduced vision.

Colour deficiency, commonly known as “colour blindness”, is the decreased ability to perceive differences in colour.

Cornea is the clear front surface of the eyeball which, together with the lens, focuses light on the retina.

Diabetic retinopathy is a common complication of diabetes and is due to damage to the small blood vessels of the retina.

Glaucoma is a disease that causes damage to the optic nerve at the back of the eye. It is often associated with elevated pressure inside the eye.

Hypermetropia or hyperopia, commonly known as “long-sightedness”, is the ability to see distances better than objects that are close.

Intra-ocular means inside the eye.

Macula is the very sensitive central part of the retina, the area at the back of the eye that provides fine vision for daily tasks such as reading, recognising faces and driving.

Myopia, commonly known as “short-sightedness”, is the ability to see close objects better than distant ones. People with this disorder may have difficulty seeing road signs, playing ball games and recognising people in the distance.

Optic nerve is the nerve that carries visual information from the retina to the brain, where what is seen by the eyes is interpreted.

Presbyopia, often called “old sight”, is increasing difficulty focusing on closer objects. It usually occurs over the age of 40 and may signal the need for reading glasses. Symptoms of this problem include a tendency to hold reading materials at arm’s length, blurred vision at normal reading distances, and fatigue, eye strain or headache when performing close work.

Retina is the thin light sensitive film inside the back of the eye. It converts light into electrical signals that travel along the optic nerve to the brain. It has a number of important functions including visual processing of the colour and shape of objects. It also contains the macula. You can’t spot eye disease. www.australia.gov.au/eyehealth

Refractive Error is when the eye fails to focus light correctly and needs a lens (for example spectacles or contact lens) to correct it.

Retinitis pigmentosa is the name of a group of genetic (inherited) eye conditions that cause the light sensitive cells in the retina to degenerate slowly and progressively, with associated discoloration of the retina.

Trachoma is a bacterial infection of the eye that can cause complications including blindness. This preventable disease is linked to poor hygiene and is often associated with poverty. Lack of facial cleanliness is the key factor that causes the spread of the infection that causes trachoma.

Visual acuity is the measure of how well the eyes can see objects from a set distance. For example, 6/60 describes the ability to see objects only at a distance of six metres, while a normal eye can see the same object at 60 metres. Normal visual acuity is 6/6 (20/20 in the imperial measure of feet). The World Health Organization defines blindness as a visual acuity of less than 3/60 (or equivalent).

Vision impairment is the partial loss of vision that is not corrected by spectacles.

Source: Department of Health and Ageing Eye Health in Australia – A background paper to the National Framework for Action to Promote Eye Health and Prevent Avoidable Blindness and Vision Loss November 2005.